This invention relates generally to waste water treatment processes, and more particularly, to processes for the recovery of acids from a waste water stream.
There has been a growing need to remove ions from aqueous solutions as required both for pollution control as well as for the recovery of valuable materials. Of particular interest are chromate wastes such as produced in electroplating plants, metal finishing plants, cooling towers and pigment manufacturing plants. These chromate wastes are extremely toxic and pose a potential threat to human and aquatic life. They also have a deleterious affect on biological sewage treatment processes. Additionally, it would be economically beneficial to recycle both the chromate ions and a resulting raffinate (depleted feed solution) to an initiating process.
Chemical treatment methods have been employed for the removal of chromates from waste water. However, such methods cannot be efficiently applied directly to the treatment of a large volume of dilute chromate solution. Similarly, the operating costs of electrochemical waste water treatment processes is significantly effected by the concentration of the pollulant to be treated. Accordingly, it is often necessary to increase the concentration of ions to be removed and to correspondingly reduce the volume of waste water to be treated so as to facilitate such removal processes.
Ion exchange processes have also been utilized for the removal and concentration of anions such as chromate ions. However, these processes are typically operated in a batch mode and require complex flow controls schemes. Moreover, both chemical and ion exchange treatments typically incur relatively high operating costs necessitated by the replacement of chemical and resin feedstocks, respectively. Similarly, electrochemical processes require an input of electrical energy which is becoming increasingly more expensive.
Accordingly, it is an object of the present invention to provide a new and improved process for removing anions from a waste water stream.
It is another object of the present invention to provide a waste water treatment process in which both treated aqueous solutions and acid solutions containing recovered anions are beneficially produced for recycling to an associated process.
It is a further object of the present invention to provide a new and improved waste water treatment process having both low energy and chemical feedstock requirements.
It is still another object of the present invention to provide a new and improved process for efficiently removing anions from a continuous flow of a dilute solution.